The capacity and performance of mobile networks may be increased through the use of heterogeneous networks in which the traditional high power macro base stations that provide wireless access over a geographic area are complemented with one or more low-powered base stations that may be deployed within the geographic area in locations where there is high demand for bandwidth. The layer of communications provided by the traditional base stations is referred to as the macro layer, and the traditional base stations are sometimes referred to as macro base stations. The low power base stations are sometimes referred to as pico or femto base stations, and generally serve a smaller geographic area (i.e., a picocell or femtocell) within a macro cell served by a macro base station.
The 3rd Generation Partnership Project (3GPP) has incorporated the concept of heterogeneous networks as one of the core items of study in the latest enhancements of the LTE standard, such as LTE Release 11 (or LTE Rel-11). Several low-powered base stations have been defined by the 3GPP for realizing heterogeneous networks such as pico base stations, femto base stations (also known as home eNodeBs, home eNBs, home base stations or HeNBs), relays, and RRHs (remote radio heads).
Dual Connectivity (DC) was introduced in LTE Release 12 for inter-frequency heterogeneous deployments, i.e. where macro and pico base stations operate on separate frequencies. The eNodeB (or eNB) base stations involved in Dual Connectivity are called the Master eNB (MeNB) and the Secondary eNB (SeNB). In Dual Connectivity, a user equipment node (UE) communicates simultaneously with both the Master eNB and the Secondary eNB. This allows the system to increase the total bandwidth of communications to/from the UE.
Cell resources provided by the Master eNB are referred to as the Master Cell Group (MCG), while cell resources provided by the Secondary eNB are referred to as the Secondary Cell Group (SCG). Both Cell Groups may consist of several cells. Signaling protocols defined by the 3GPP enable a total of 5 cells to be included in a Master Cell Group and in a Secondary Cell Group.
The 3GPP also defines the so-called Closed Subscriber Group (CSG) concept. A Closed Subscriber Group is made of a number of UEs that have privileged access to those cells that transmit a CSG Identifier (CSG ID) that identifies the group. A cell that supports the Closed Subscriber Group functionality can be categorized as one of a closed access type or a hybrid access type. Closed access cells are cells in which only UEs that are member of the Closed Subscriber Group corresponding to the CSG ID transmitted by the cell can enter. Hybrid access cells are cells in which those UEs that are members of the Closed Subscriber Group associated with the CSG ID transmitted by the cell may be prioritized with respect to other UEs. That is, for a hybrid access cell, Closed Subscriber Group member UEs of may enjoy better quality of service (QoS) than other UEs attempting to access the same cell.
The membership status to a given Closed Subscriber Group for a given UE determines whether the UE is member or non-member of the Closed Subscriber Group, and therefore determines whether the UE can access a closed access CSG cell or whether the UE can be prioritized in a hybrid access CSG cell.
Closed Subscriber Groups can be supported by Home eNBs as well as by any other base station in the system.
In LTE Release 13, some of the ongoing work items aims to add requirements, and, if needed, respective solutions for the support of Closed Subscriber Groups for dual connectivity.
The approaches described in the Background section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in the Background section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in the Background section.